Studies On The Amounts And Activity Of Methanogens In The Soil Of Rice-Duck Complex Ecosystem

The study adopted the technology of anaerobic culture case technique, MPN(most probable number) and roll tube methods, and gas chromatography to survey the amounts of methanogens in soil of rice-duck complex ecosystem of wetland, the influence of methamidophos and acetochlor on the amounts and activity of methanogens in soil of this system, the residual quantity of methamidophos in soil of rice-duck complex ecosystem of wetland, and the segregation and cultivate characteristic of dominant methanogens in paddy fields. It aimed at affording scientific basis for coordinating the conflict between rice production and environmental protection, and searching for ideal measure to mitigate methane emission and achieve agricultural sustainable development. Main results for this study are as follows:1. The study on the amounts of methanogens in the soil of rice-duck complex ecosystem of wetland.There is no report in this respect so far. The results indicated: The seasonal change pattern of the amounts of methanogens in the soil of rice-duck complex ecosystem of wetland and CK (ordinary system ) was consistent with that of methane emission law of paddy fields. The amounts were the greatest at active tillering stage and booting stage for early rice, and the amounts were the greatest at active tillering stage for late rice. Rice-duck complex planting and breeding pattern greatly decreased the amounts of paddy fields, especially decreased the amounts of methanogens during methane emission peak period. The amounts of that in the soil of early rice and late rice were decreased 20%~96.9% and 94.3%~95.8% by the MPN method, the amounts of that were decreased 33.3%~98.1% for early rice by the roll tube method. It confirmed that the amount of methanogens was the one of main factors of amount of methane emission in paddy fields.2. The study on the segregation and characterization of dominant methanogens in paddy fields.The result showed: Four strains which were dominant were isolated from the soil of early rice at the experiment farm in Changsha County of Hunan Province by anaerobic culture case and roll tube method, and were named strain 201, 202, 203and204. There were different morphology and physiological characteristic. The colony of strain 201, 202 and 203 were round, and colony of strain 204 was notregular, strain 201 and 204 brought about yellow fluorescence, but strain202 and 203 brought about blue fluorescence. Strain 201 and 202 could use H2/CO2, nonemethylamine, sodium acetate, isopropanol and formate, strain 202 could also use methanol; strain 203 and 204 could use H2/CO2, nonemethylamine, methanol, strain 203 could also use isopropanol, strain 204 could also use sodium acetate. The optimum pH of strain 201 and 204 was 6.5,that of strain 202 was 7.5, and that of strain 203 was 8.0. The optimum temperature of strain 201 was 35 ,that of strain 202 and 204 was 40 ,and that of strain 203 was 45 .3. The influence of methamidophos and acetochlor on the amounts and activity of methanogens in the soil of rice-duck complex ecosystem of wetland.The result indicated: when the concentration of methamidophos solution was 0.1, 0.2, 0.5, l.0mg/kg respectively, the growth of methanogens was stimulated in 7 days, the amounts of that increased 0.2-44.1 times, and the production of methane per tube was increased 0.8-2.1 times. The growth of methanogens was obviously inhibited in 7 days at four concentration of acetochlor solution, the amounts of methanogens were decreased 50%~99%, and the production of methane per tube was decreased 2.9-207 times. The stimulating and retarding effect was more obvious with increasing concentration of methamidophos and acetochlor solution respectively. With prolonging of time adding pesticide, the amounts and activity of methanogens had recovered normal level step by step. Author suggested that methanogens were sensitive bacteriums on pesticides.4. The study on the residual quantity of methamidophos in the soil of rice-duck complex ecosystem of wetland.The result showed: there...